Matrix for electroforming foraminous sheets



Patented Feb. Il, 1941" UNITED sTATE'sg MA'rmx 'Fon ELEcraoFonmNG FoaAMlNoUs snEE'rs Edward o. Norris, Westport, conn., mignonto Edward O. Norris, Inc., New York, N. Y., a corporation of New York Application April 21, 1938, Serial No. 203,235

'l Claims. (Cl. 204-11) My present invention relates to matrices. and more particularly to an improved matrix and the method of making the same.

In my issued Patents 2,166,366 and 2,166,367,

5 both issued July 18, 1939, I have describedand claimed the improved method of making a matrix on which may be electro-deposited a suitable metal, such as copper, to form a foraminous plate or sheet. My present invention, as regards the l method of making a matrix, andthe resulting matrix, while somewhat analogous to those of my co-pending applications referred to, is an improvement thereover.

According to my present invention, as in the l inventions described and claimed in my co-pending applications referred to, I produce a matrix having a face of electrically conductive material arranged in the form of any desired pattern and with the material between the lands of the pattern comprising material that presents a surface inactive to electrolytic deposition, such as llings of commercial Bakelite, or other similar phenolic condensation product, asphaltum, natural and synthetic rubber, or a thick plating of chromium (say .001") on metal'. Such material I will term hereinafter passive material."

As a part of my invention, I describe an improved means of locking the passive material to the matrix and thus produce a matrix on which foraminous sheets or plates may be electrodeposited and then stripped therefrom without injury to the matrix.

Generally described, the object of the invention is an improved matrix adapted for producing by electro-deposition foraminous sheet material and having the characteristics of durability, so that repeated deposits may be made thereon and stripped therefrom, and also cheapness of production and resistance to disintegration by corrosion.

Another object consists in a method of producing such a matrix. y

In the accompanying drawing:

Fig. 1 is a section through a portion of a matrix and illustrating the first step of my improved method; y

Fig. 2 is a section through a portion of a matrix and illustrating another step of my improvedv method; f

Fig. 3 is a section through a portion of a matrix and illustrating a further step of my improved method: y

Fig. 4 ls a section through a portion of a complete matrix made according to my-`improved method; Fig. 5 is a perspective view of a complete matrix partly in section, made according to my improved method.

In producing a matrix according to my present invention, a metallic plate or matrix base I0 composed, for example, of copper and produced in any desired manner, such as by the photo-printing and vetching method described in my Patent No. 2,166,366, ls provided on one face for instance with a, plurality of lands Il arranged, if a square mesh foraminous sheet is to be made, at right angles to each other so as to exhibit a surface having the pattern of a network of interconnected lands separated by depressions or pits I2. While the lands are preferably arranged at right angles to each other, I may arrange them at any other desired angle and the showing therefore is to be considered as merely illustrative. Proceeding with the plate thus described,

.the pitted face thereof is treated by coating it with shellac I3 so that the surfaces. of the pits and the lands are entirely covered. 'Ihe surface of the plate is then treated by'rubbing or'grinding, or a like method, until the shellac is completely removed from the surfaces of the lands. The next step consists in covering the entire surface of the plate, including the shellac-covered' surfaces of the pits and the exposed metallic surface of the lands, with conducting material I4 to which an electrolytic deposit thereon does not adhere with enough tenacity to preventv it from being readily stripped oil'. An example of a suitable substance for the purpose is a mixture of wax and graphite having about the consistency of thin paste. vThis paste is applied to the face of the plate I0, entirely covering the lands and the surfaces of the pits, and thus serving as a depositing surface to which, however, the deposit does not tenaciously adhere. As an alternative to this procedure, the wax may iirst be applied, and, after it is thoroughly rubbed out thin, the graphite or bronze powder or some other electrically conductive powder may be dusted over the surface.

I'he next step is to employ the plate thus prepared as a cathode in an electrolytic bath and deposit thereon the layer |5-say of copper, building up the deposit to a substantial thickness in the order, for example, of .005" or .010". Those parts of the plate which are to be excluded from Referring to Fig. 2, the base plate is shown with an asphaltumI mask Il to protectit against electrolytic action and with the depressions I1 `l5 washed out with alcohol or other suitable solvent and the plate is then employed as a depositing surface onvwhich to electroform the layer 2I. If the plate III and the built-up portions I I are of copper, the deposit 2| should be of material that is-not aected by a re-agent that corrodes copper or,` more generally speaking, the plate I5 with its built-,up portions I9 must be capable of removal from the deposit 2| by some agency, presently to be referred to, that acts selectively on it to the exclusion of action on the nickel. It is to be noted that the process carried to the point shown in Fig. 2 has resulted in protuberances I9 that are peripheraliy grooved as shown at 20. Therefore, the nickel deposit 2I conforms to the surface contour of these grooves as well as to the surface contour of the remaining areas of the plate I5, resulting in depressions', about each wall of which there is an inwardly extending overhanging ledge or shoulder 25.

After removing the asphaltum mask I8, the copper plate I5 and its protuberances I9 may be removed by electrolytic deplating in a bath su ch that the nickel is not affected, or by the application of (l) a solution of potassium cyanid, or

(2) a mixture of chromic and sulphurlc acids in water, suitable -proportions being about as follows:

Either of these agents acts on the copper to the exclusion of the nickel.

The entire metallic surface of the -nickel deposit now being exposed, the nickel deposit may be strengthened by the deposit 22 of copper. A coating of shellac 23 may be applied to the copper to mask the copper against electrolytic deposit when subjected to an electrolytic bath for the production of foraminous sheet.

The structure thus far described is illustrated 'in Fig. 4, where the numeral 24 indicates depressions, and the numeral 25 indicates the peripheral ledges on the walls of the depressions.

'Ihe depressions 2l may now be filled with passive material 21 consisting,V for example, of Bakelite, and the entire surface rubbed to as perfect a plane as possible, leaving lands 26 of exposed metal defining the pattern of the foraminous sheet to be produced and with the passive material 21. This composite plate may then be employed as a cathode in an electrolytic bath e for the deposition of foraminous sheet. It is, of course, necessary prior to the latter step that a 7 stripping film be applied to the lands 26, of such a character that while the lands will receive a deposit, the deposit will not adhere tenaciously enough to prevent ready stripping.

As regards the passive material 21, it will be 1| noted that the mass is firmly locked in position by the ledges 2l, and for this reason the matrix will withstand continued and repeated use.

In producing the matrix, it is desirable to provide for a salvage edge along the borders thereof, as it is usual to produce foraminous sheet in s which openings do not extend' to' the' extreme limit of the sheet. It is' desirable, therefore, to provide on the upper peripheral face'a cutaway portion 2l. Thiscutaway portion is coated with the wax and graphite mixture I4 and as a result 10 the layer Il has a portion 29 which conforms to the shape of the cutaway portion. In the nnished matrix this cutaway portion is duplicated in the layer 2 I, as indicated by the reference numeral 30 and'is filled with insulating material as 15 indicated by the reference numeral 1I in Fig. 4. \I have described above certain embodiments of my invention and a preferred process with certain modifications thereof, but I wish it to be understood that these are illustrative and not 20 limitative of my invention and that I reserve the right to make various changes in form, construcplurality of projections on one face thereof, coat- 30 ing the surface of thevplate of metal around the base of the projections with a non-conductive material, electro-depositing metal on the surface of the projections to an extent to overlie the nonconductive material, removing the non-conduc- 35 tive material and then depositing a layer of Y metal on the surface of the plate having the projections thereon, and then dissolving the plate of metal.

2. The improved method of making a matrix, 40 which comprises forming a plate of metal with a plurality of projections on one face thereof, coating the surface of the plate around the base of the projections with a non-conductive material, electro-depositing metal on the surface of 45 the projections to overlie the non-conductive material, removing the non-conductive material from the plate, depositing a layer of metal on the surface of the plate of metal and on the projections, dissolving the plate of metal, and then 50 filling the depressions in the layer of metal with non-conductive material.

3. The improved method of making a matrix, which comprises forming a plate of metal with a plurality of projections onv one face thereof, coat- 55 ing the surface of said plate of metal around the base of the projections with a soluble non-conductive material, electro-depositing metal on the surface of the projections to form a peripheral shoulder around each projection, removing the 60 soluble non-conductive material, depositing a layer of metal on the surface of the plate having the projections thereon, removing the plate of metal, and filling the depressions in the layer of metal with insulating material. 65

4. The improved method of making a matrix, which comprises forming a plate of metal'with a plurality of projections on one face thereof, coating the surface of said plate around the base of the projections with a soluble non-conductive 10 material, electro-depositing metal on the exposed surface of the projections to accentuate the height of the projections and form a peripheral groove around each projection, dissolving the soluble non-conductive material, depositing a 'Il layer of metal on the surface of the plate of metal having thel projections thereon to produce a matrix base, dissolving the plate of metal so that only the layer of metal remains, and iilling the depressions in the layer of metal with insulating material.

5. In the improved method of making a matrix -having one face thereof provided with a plurality of indentatlons arranged in any desired pattern and with each indentation isolated from every other indentation, the steps which comprise making a master plate by electro-depositing metal and in which the indentations which aretoappearinthematrixassumetheformof projections, coating the face of the master plate around the base of the projections with a nonconductive material, electro-depositing metal on the face of the master plate and on the projections to accentuate the height of the projections and form circumferential grooves around each projection, removing the non-conductive ma terial, depositing a layer of metal on the master plate, and then removing the master plate.

6. The improved method of making a matrix. which comprises forming a plate of metal with a plurality of projections thereon, coating the surface of the plate around the base of the projections with a soluble non-conductive material,

electro-depositing metal on the exposed surface oi the projections on the plate of metal to accentuate the height of the projections and form a peripheral groove around each projection, dissolving the soluble non-conductive material, depositing a layer of'metal on the surface of the plate of metal having the projections thereon to produce a matrix. dissolving the plate of metal so that only the matrix remains, and filling the depressions in the matrix with insulating material.

'1. The improved method oi' making a matrix for the electrodeposition of foraminous sheet,

which comprises forming a plate of metal withA a plurality of protuherances on one face thereof, coating the said face around the bases of the projections with electrically non-conductive material, electrodepositing metal on the surface of the protuberances to form a peripheral shoulder around each protuberance, removing the electrically non-conductive material, electrodepositing a layer of metal on that surface of the plate on which the protuberances are located, removing the mst-mentioned plate with its protuberances, and filling the depressions in the last'- mentioned plate with electrically non-conductive' material.

EDWARD 0. NORRIS. 

